8 American Midland Naturalist Monograph No. 2 



SYSTEMATIC TREATMENT 

 Key to the Sections 



Group I. Seed Plants. Plants normally reproducing by seeds containing an embryo. 

 Gymnosperms and Angiosperms. 



A. Herbaceous Plants 



1. Plants grasses, sedges, or rushes; perianth green or absent Section I, p. 9 



1. Plants not grasses, sedges, or rushes. 



2. Terrestrial plants, not floating on or submerged in water; sometimes growmg at the 

 edge of water but then usually erect. 

 3. Leaves compound, composed of few or many leaflets, or divided to the midrib 



or base Section 2, p. 9 



3. Leaves simple, sometimes lobed, but the lobes not extending to the midrib or base 



(leaves rarely absent or reduced to spines or scales). 



4. Stems not climbing or twining; tendrils absent; plants never cacti or cactus-like. 



5. Plants green, normally possessing chlorophyll, not parasitic or saprophytic 



or noticeably so. 



6. Plants without a leafy stem, or the stems underground, the flower-stalks 



leafless, or with a single leaf or a pair or whorl of leaves subtending the 



inflorescence Section 3, p. 11 



6. Plants with leafy stems, the leaves sometimes reduced to scales; stem some- 

 times with only a single leaf, but this borne far below the inflorescence. 

 7. Leaves evidently parallel-veined; mostly Monocotyledons (except 

 Er\]ngium and Tragopogon) with the floral parts, or some of them 

 in threes, not in fives; stem in cross-section showing the vascular 

 bundles irregularly distributed throughout the pith or around a central 



cavity; cotyledon 1 Section 4, p. 13 



7. Leaves not evidently parallel-veined, almost always net-veined (or 

 sometimes apparently only 1 -veined); mostly Dicotyledons (except 

 Trillium and Smilax) with the floral parts often in fives or fours, 

 only exceptionally in threes; stem in cross-section showing a central 

 pith (or, in hollow stems, a cavity) surrounded by a circle of vascu- 

 lar bundles; cotyledons 2. 

 8. Leaves, or at least some of them, opposite or whorled. 



9. Leaves entire Section 5, p. 13 



9. Leaves more or less toothed or lobed Section 6, p. 16 



8. Leaves alternate. 



10. Leaves entire Section 7, p. 17 



10. Leaves toothed (or sinuate) or lobed SECTION 8, p. 19 



5. Plants parasitic or saprophytic, without chlorophyll; leaves reduced to scales; 



fruit a capsule Section 9, p. 21 



4. Stems either twining or climbing (tendrils sometimes present) ; or else cactus 



plants with conspicuously jointed, succulent, spiny stems Section 10, p. 21 



2. Aquatic plants, floating on or submerged in water (or sometimes growing on muddy 

 or sandy shores) Section II, p. 22 



B. Trees and Shrubs (including woody climbers and trailers) 



1 1 . Gymnosperms (except Huchonia) . Leaves needle-Iike (acicular), scale-like, or subu- 

 late, evergreen (deciduous in Laiix and 1 axojiiini) SECTION 19, p. 31 



I 1 . Angiosperms. Leaves not as above; "broadleaf" trees and shrubs. 

 12. Flowers appearing with or after the leaves. 



13. Leaves opposite or whorled SECTION 12, p. 23 



